1. Technical Field
This invention relates to a process for preparing phosphine oxides having the general formula (2) which comprises reacting iminophosphoranes having the general formula (1) with phosphorus oxytrichloride and to a process of purifying the above described phosphine oxides. The present inventors previously found that the above described phosphine oxides are very effective as polymerization catalysts for polymerizing alkylene oxide compounds, as catalysts for producing oxyalkylene derivatives from epoxy compounds, or as curing catalysts for curing the raw material resin for IC sealing, and already filed an application for a patent on each of the above described catalysts (Japanese Patent Application No. 10-106745, Japanese Patent Laid-Open Nos. 11-302371 or 11-322901, etc.).
2. Prior Art
Except for the present inventors"" patent documents, the only publicly-known literature on phosphine oxides having the general formula (2) is the one disclosed by G. N. Koidan et al., in Journal of General Chemistry of the USSR, 55, p1453 (1985).
In this literature, the compound referred to as iminotris(dimethylamino)phosphorane in this patent application, which is iminophosphorane having the general formula (1) whose R is a methyl group, is termed hexamethyltriamidophosphazo hydride and the compound referred to as tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide in this patent application, which is phosphine oxide having the general formula (2) whose R is a methyl group, is termed tris[tris(N,N-dimethylamido)phosphazo]phosphate.
And the compound referred to as aminotris(dimethylamino)phosphonium chloride in this patent application, which is aminophosphonium chloride having the general formula (3) whose R is a methyl group, is the same as the compound termed hexamethyltriamidophosphazo hydride hydrochloride and shown by the form of [HN=P(NMe2)3].HCl in the above described literature. Hereinafter, for the above described three kinds of compounds the expressions of this application shall be used.
In the above literature, described is the reaction of tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide with methyl iodide. And a process for preparing tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide, the raw material of the above reaction, is disclosed.
The literature states that tris[tris(dimethylamino)phosphoranilidenamino]phosphine oxide was obtained in an isolation yield of 85% by, first, adding a solution of phosphorus oxytrichloride in petroleum ether to a solution of iminotris(dimethylamino) phosphorane in petroleum ether drop by drop at 20xc2x0 C. for 30 minutes while stirring the solution mixture so that the mole ratio of the above described phosphorane to phosphorus oxytrichloride becomes exactly 6:1, after that (the time is not specified), separating the precipitate of aminotris(dimethylamino)phosphonium chloride as a by-product, washing the above described precipitate with petroleum ether, concentrating the filtrate, followed by crystallizing the residue from a small amount of the petroleum ether.
However, when the present inventors carried out the preparation of tris(tris(dimethylamino)phosphoranilidenamino phosphine oxide under the same conditions as above, even after the addition of phosphorus oxytrichloride at 20xc2x0 C. for 30 minutes, almost no object compound was produced, as shown in comparative example 5 below. After that, the reaction was proceeded at a raised temperature of 40xc2x0 C. for 24 hours, however, the reaction yield of the object compound was as low as about 60%. Even after an additional 48 hours of reaction, the reaction yield was about 73% at the most.
In addition, the above literature only states that tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide was obtained xe2x80x9cby crystallizing the residue from a small amount of the petroleum etherxe2x80x9d, but does not describe in detail the recrystallization process. The present inventors attempted recrystallization of crude phosphine oxide in such a manner that, first precipitate was separated by filtration from the liquid reaction product obtained after the 48 hours"" reaction at 40xc2x0 C., as described above, then the filtrate was concentrated to dry to become a solid.
As shown in comparative example 6 below, a small amount of crystal deposition was observed only after the filtrate was cooled to xe2x88x9210xc2x0 C., and the crystal could be finally gathered after the filtrate was cooled to an extremely low temperature of xe2x88x9220xc2x0 C. The isolation yield of the crystal, that is, the isolation yield of tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide was as low as 20%, and moreover, the crystal contained a large amount of chlorine ion (about 600 ppm). Such residue of chlorine ion is a very serious problem when the above described phosphine oxide is used as a curing catalyst for curing the raw material resin for IC sealing which is required to have an electrical insulating property.
In the case where tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide is prepared by reacting iminotris(dimethylamino) phosphorane with phosphorus oxytrichloride, if one molecule of iminotris(dimethylamino) phosphorane reacts with one molecule of phosphorus oxytrichloride, one molecule of hydrogen chloride is yield at the same time. This hydrogen chloride immediately reacts with iminotris(dimethylamino) phosphorane to yield ionic aminotris(dimethylamino)phosphonium chloride. Accordingly, 6 moles of iminotris(dimethylamino) phosphorane is required stoichiometrically so as to react all of the three chlorines of one mole of phosphorus oxytrichloride. This is expressed by the following reaction equation.
6HNxe2x95x90P(NMe2)3+Oxe2x95x90PCl3xe2x86x92Oxe2x95x90P[Nxe2x95x90P(NMe2)3]3+3[H2Nxe2x80x94P+(NMe2)3]Clxe2x88x92
As shown in comparative example 7 below, in the purifying process described in the above described literature, when imino(dimethylamino) phosphorane was used in excess of that stoichiometrically required so as to increase yields, the unreacted residue of the above described phosphorane could not be removed sufficiently, which led to a decrease in purity of recrystallized tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide.
Thus, the above disclosed process for preparing: tris[tris(dimethylamino)phosphoranylidenamino]phosphine oxide is still very insufficient as an industrial process in that: its reaction and isolation yields are low, the purification process for its product requires an extremely low temperature, the ionic compound yielded by its reaction cannot be removed sufficiently, and its unreacted raw material cannot be removed sufficiently when using one reactant in excess of that stoichiometrically required in order to increase yields.
Accordingly, it is a primary object of the present invention to provide a process for preparing phosphine oxides having the general formula (2) in a raised yield which comprises reacting iminophosphoranes having the general formula (1) with phosphorus oxytrichloride.
Another object of the present invention is to provide a process for purifying the above described phosphine oxides which makes it possible in an industrially more realistic manner to remove unreacted raw materials and ionic impurities in a liquid reaction product and to provide a high yield and purity of the above described phosphine oxides.
After continuously concentrating their energies on investigating processes for preparing and purifying the above described phosphine oxides so as to achieve the above objects, the present inventors finally found that in the process for preparing phosphine oxides having the general formula (2) which comprises reacting iminophosphoranes having the general formula (1) with phosphorus oxytrichloride, the use of an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. instead of petroleum ether (with permittivity 1.85 to 1.95 at 20xc2x0 C.), as a reaction solvent, increases the reaction rate remarkably and gives the above described phosphine oxides in a high yield.
In addition, it was found that, although one part by weight of petroleum ether is a good solvent to dissolve 1.5 parts by weight or more of the above described phosphine oxides, when the liquid reaction product reacted in a petroleum ether as a reaction solvent is washed with a small amount of water, almost all amount of the above described phosphine oxides moves to a water phase and there is almost none left in a petroleum ether phase.
Surprisingly, however, it was found that in a liquid reaction product obtained by using a specific solvent, such as o-dichlorobenzene, almost all amount of the above described phosphine oxides is left in an organic phase even after water-washing and almost all amount of the aminophosphonium chlorides having the general formula (3) which are yielded by the reaction and the unknown compounds as by-products move to a water phase, as shown in example 8 below. Further surprisingly, it was also found that, when iminophosphoranes are used in a stoichiometrically required amount or in excess of the same amount, almost all amount of the iminophosphoranes having the general formula (1) which are left unreacted in the liquid reaction product move to a water phase.
As described above, the present inventors found that the use of an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. as a reaction solvent is effective in increasing the reaction rate as well as the reaction yield, as a result, producing the phosphine oxides having the general formula (2) in a high yield, and in increasing the purity of the above described phosphine oxides simply by water-washing the solution containing the above described phosphine oxides and a specific organic solvent while keeping the isolation yield almost the same. Thus the present invention was completed.
Accordingly, the first aspect of the present invention is a process for preparing phosphine oxides having the following general formula (2): 
wherein R represents the same kind or different kinds of hydrocarbon group(s) with 1 to 10 carbon atom(s), and two Rs on the same nitrogen atom can combine with each other to form a ring structure, which comprises reacting iminophosphoranes having the following general formula (1): 
wherein R is the same as that of the formula (2), with phosphorus oxytrichloride, in the presence of an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. as a reaction solvent.
The second aspect of the present invention is a process for purifying phosphine oxides which comprises water-washing a solution containing at least phosphine oxides having the general formula (2) and an organic solvent which does not substantially mix with water to give the above described phosphine oxides as a solution, or concentrating to dry the above described solution to give the above described phosphine oxides as a solid.
In the preparation and purification processes of the present invention, the chemical structure of phosphine oxides is expressed by the general formula (2); however, the formula just expresses one canonical structure. According to the formula (2), a double bond is formed between phosphorus atom and oxygen atom; however, phosphine oxides may have another canonical structure where electrons cluster on the side of oxygen atom to form an anion of oxygen and a cation of phosphorus (P+xe2x80x94Oxe2x88x92). The cation of phosphorus may be delocalized through a conjugated system. It should be understood that phosphine oxides having the formula (2) in the preparation and purification processes of the present invention are resonance hybrids including all of the above described structure.
In the preparation and purification processes of the present invention, R of iminophosphoranes having the general formula (1), of phosphine oxides having the formula (2) and of aminophosphonium chlorides having the formula (3) represents the same kind of or different kinds of hydrocarbon group(s) with 1 to 10 carbon atom(s). In particular, the R represents an aliphatic or aromatic hydrocarbon group such as methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, tert-butyl, 2-butenyl, 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, isopentyl, tert-pentyl, 3-methyl-2-butyl, neopentyl, n-hexyl, 4-methyl-2-pentyl, cyclopentyl, cyclohexyl, 1-heptyl, 3-heptyl, 1-octyl, 2-octyl, 2-ethyl-1-hexyl, 1,1-dimethyl-3,3-dimethylbutyl (commonly known as tert-octyl), nonyl, decyl, phenyl, 4-toluyl, benzyl, 1-phenylethyl, or 2-phenylethyl.
When two Rs on the same nitrogen atom of iminophosphoranes having the general formula (1), of phosphine oxides having the formula (2) and of aminophosphonium chlorides having the formula (3) combine with each other to form a ring structure together with the nitrogen atom, the formed cyclic amino groups are cyclic secondary amino groups containing 4 to 6 carbon atoms on the ring, and xe2x80x94NR2""s are cyclic secondary amino groups of 5 to 7 members including a nitrogen atom.
The above described cyclic secondary amino groups include, for example, pyrrolidine-1-yl group, piperidine-1-yl group, morpholine-4-yl group, and substitution products thereof substituted with alkyl groups such as methyl group and ethyl group.
All of or part of the potential nitrogen atoms of the above described iminophosphoranes, phosphine oxides and aminophosphonium may participate in the formation of such a ring structure.
R is preferably an aliphatic hydrocarbon group with 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, tert-pentyl, or 1,1-dimethyl-3,3-dimethylbutyl, and more preferably a methyl group.
The above described iminophosphoranes having the general formula (1) can be synthesized in the same manner as the description in EP-0921128 or G. N. Koidan et al., Zh. Obshch. Khim., 50, 679-680 (1980). Of the above described iminophosphoranes, the one whose R is a methyl group is commercially available.
The first aspect of the present invention is a process for preparing phosphine oxides having the formula (2) which comprises reacting iminophosphoranes having the general formula (1) with phosphorus oxytrichloride, wherein an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. is used as a reaction solvent.
The preparation process of the present invention is characterized by use of an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. as a reaction solvent. The use of an aprotic organic solvent with permittivity less than 2.2 at 20xc2x0 C. as a reaction solvent causes an extreme decrease in reaction rate under the same mild conditions. On the other hand, if the reaction temperature is raised so as to increase the reaction rate, a side reaction proceeds, as a result of which phosphine oxides having the general formula (2) cannot be obtained in a high yield.
The aprotic organic solvents with permittivity less than 2.2 at 20xc2x0 C. include, for example, petroleum ether (1.85 to 1.95; permittivity at 20xc2x0 C. and so on), hexane (1.89), decane (1.99), 1-hexene(2.06), 1-octene (2.08), cyclohexane (2.05) and decalin (2.19), all of which are not preferable as a reaction solvent of the present invention.
Concrete examples of the aprotic organic solvents with permittivity 2.2 or more at 20xc2x0 C. used in the preparation process of the present invention as a reaction solvent include, for example, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane, 1,1-dichloroethane or hexachloroethane; aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, normal propylbenzene, cumene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, 1,4-diethylbenzene, 1,3-diisopropylbenzene or dodecylbenzene; halogenated aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, bromobenzene, o-dibromobenzene, 1-bromo-2-chlorobenzene, 1-bromonaphthalene, 1-chloronaphthalene, 2-chlorotoluene, 2-bromotoluene, 2,4-dichlorotoluene, 1-bromo-2-ethylbenzene, 2-chloro-o-xylene or 1,2,4-trichlorobenzene; ethers such as diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, diethylene glycol dimethyl ether, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, anisole or phenetol; esters such as methyl formate, ethyl formate, propyl formate, isobutyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl benzoate, isopentyl benzoate or ethyl cinnamate; nitro compounds such as nitromethane, nitroethane or nitrobenzene; and polar compounds such as acetonitrile, propionitrile, benzonitrile, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide or hexamethylphosphorictriamide. For further details, refer to Teruzo Asahara et al. Handbook of Solvents (Tokyo: Kodansha Publishing Company, 1982).
Any other aprotic organic solvents may be used, as long as their permittivity is 2.2 or more at 20xc2x0 C. and they do not hinder the preparation process of the present invention. These aprotic organic solvents may be used independently or jointly. Further, the aprotic organic solvent system which is a mixture of the above described aprotic organic solvents and the aprotic organic solvents with permittivity less than 2.2 at 20xc2x0 C. and allowed to have permittivity of 2.2 or more at 20xc2x0 C. should be understood as an xe2x80x9caprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C.xe2x80x9d in the preparing process of the present invention.
Of these aprotic organic solvents, preferable are those which do not dissolve aminophosphonium chlorides having the formula (3) described below. The preferable aprotic organic solvents include, for example, aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, normal propylbenzene, cumene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, 1,4-diethylbenzene, 1,3-diisopropylbenzene or dodecylbenzene; halogenated aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, bromobenzene, o-dibromobenzene, 1-bromo-2-chlorobenzene, 1-bromonaphthalene, 1-chloronaphthalene, 2-chlorotoluene, 2-bromotoluene, 2,4-dichlorotoluene, 1-bromo-2-ethylbenzene, 2-chloro-o-xylene or 1,2,4-trichlorobenzene; and ethers such as diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, diethylene glycol dimethyl ether, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, anisole or phenetol.
Of the above described aprotic organic solvents, more preferable are those substantially immiscible with water as described in the purification process of the present invention. The aprotic organic solvents substantially immiscible with water include, for example, aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, normal propylbenzene, cumene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, 1,4-diethylbenzene, 1,3-diisopropylbenzene or dodecylbenzene; and halogenated aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, bromobenzene, o-dibromobenzene, 1-bromo-2-chlorobenzene, 1-bromonaphthalene, 1-chloronaphthalene, 2-chlorotoluene, 2-bromotoluene, 2,4-dichlorotoluene, 1-bromo-2-ethylbenzene, 2-chloro-o-xylene or 1,2,4-trichlorobenzene. And more preferable are toluene, chlorobenzene, dichlorobenzene or 2,4-dichlorotoluene.
The amount of these aprotic organic solvents used is not expressly restricted; however, it is normally 500 weight parts or less per 1 weight part of phosphorus oxytrichloride as a raw material, preferably 1 to 100 weight parts, and more preferably 1.5 to 50 weight parts. It is not a problem that part of the liquid phosphorus oxytrichloride can be immiscible with these aprotic organic solvents.
In the preparation process of the present invention, the mole ratio of iminophosphoranes having the formula (1) used to phosphorus oxytrichloride is not expressly restricted; however, it is normally 5 to 12, preferably 6 to 10, and more preferably 6.1 to 8.0.
The reaction temperature varies depending on the amount of solvent used, on the mole ratio of the raw materials, etc.; however, it is normally xe2x88x9210 to 200xc2x0 C., preferably 0 to 150xc2x0 C., and more preferably 15 to 100xc2x0 C. In the reaction, the set temperature may be changed phase by phase; for example, the reaction may be carried out at a relatively low temperature in the beginning and at a relatively high temperature in the last.
The reaction may be carried out under reduced pressure, under normal pressure and under pressure; however, it is normally carried out under normal pressure. The reaction time varies depending on the reaction temperature and other factors; however, it is normally 0.1 to 100 hours, preferably 0.5 to 50 hours, and more preferably 1 to 30 hours.
In the liquid reaction product thus obtained, aminophosphonium chlorides having the formula (3) can sometimes be deposited as a solid and can sometimes be dissolved depending on the kind or amount of the solvent used or on the kind of iminophosphoranes having the formula (1). The methods of removing the above described phosphonium chlorides in such states are not restricted to specific ones and any methods can be used to remove them; however, when the above described phosphonium chlorides are deposited in the liquid reaction product as a solid, the method in which the liquid reaction product directly undergoes a solid-liquid separation is normally used; and when the above described phosphonium chlorides are dissolved in the liquid reaction product, first the solvent used is distilled from the liquid, then another organic solvent which does not dissolve the above described phosphonium chlorides is added, and the liquid reaction product can undergo a solid-liquid separation.
The above solid-liquid separation can be conducted using any methods; however, general-purpose methods such as filtration, centrifugation and decantation are normally used. Of the above methods, filtration is most preferable. If needed, filter cake can be washed with the above described aprotic organic solvent or an organic solvent which does not dissolve the above described phosphonium chlorides, and the washings may be added to the filtrate.
The organic solvents which do not dissolve the above described phosphonium chlorides include, for example, saturated aliphatic hydrocarbons such as normal pentane, normal hexane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, normal heptane, normal octane, 2,3,3-trimethylpentane, isooctane, normal nonane, 2,2,5-trimethylhexane or normal decane; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, p-menthane, bicyclohexyl or decalin; aromatic hydrocarbons such as. benzene, toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, normal propylbenzene, cumene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, tetralin, butylbenzene, p-cymenel cyclohexylbenzene, 1,4-diethylbenzene, 1,3-diisopropylbenzene or dodecylbenzene; halogenated aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, bromobenzene, o-dibromobenzene, 1-bromo-2-chlorobenzene, 1-bromonaphthalene, 1-chloronaphthalene, 2-chlorotoluene, 2-bromotoluene, 2,4-dichlorotoluene, 1-bromo-2-ethylbenzene, 2-chloro-o-xylene or 1,2,4-trichlorobenzene; and ethers such as diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, diethylene glycol dimethyl ether, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, anisole or phenetol. The organic solvents which do not dissolve the above described phosphonium chlorides are, however, limited to the above described ones.
The above described phosphonium chlorides separated as solids can be re-formed as iminophosphoranes having the formula (1) by the method described in EP-0921128 or G. N. Koidan et al., Zh. Obshch. Khim., 50, 679-680 (1980) and recycled as part or the whole of the iminophosphoranes having the formula (1) in the preparation process of the present invention.
In the mother liquor from which the aminophosphonium chlorides having the formula (3) have been removed, there exist iminophosphoranes having the formula (1) which remain unreacted or are added in excess. The methods of removing the above described phosphoranes are not restricted to specific ones and any methods can be used to remove them; however, normally used are the method in which the above described mother liquor is concentrated to dry and the above described phosphoranes are distilled off under normal pressure or under reduced pressure and the method in which the above described mother liquor is washed with water as described below.
The dried solid and the solution having undergone water washing thus obtained contain phosphine oxides having the formula (2) of a sufficiently high purity. Although they can sometimes be used as they are for next purpose, they can sometimes be used as a concentrated solution or a solid by removing a small amount of water contained therein with a drying agent or by distillation or, in case of solutions having undergone the above described water washing, by removing part of or the whole solvent used.
The second aspect of the present invention is a process for purifying phosphine oxides having the formula (2) which comprises water washing a solution containing at least the above described phosphine oxides and an organic solvent substantially immiscible with water to give the above described phosphine oxides as a solution, or further comprises concentrating to dry the above described solution to give the above described phosphine oxides as a solid.
xe2x80x9cThe organic solvents substantially immiscible with waterxe2x80x9d used in the purification process of the present invention mean organic solvents conventionally used for extraction etc. which dissolve in water too little to be taken into consideration and can be easily separated from water phase. In addition, the partition rate of their phase to water phase is high in terms of phosphine oxides having the formula (2), and they cause no chemical process even if they come in contact with the above described phosphine oxides. The organic solvents substantially immiscible with water as described above include, for example, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane, 1,1-dichloroethane or hexachloroethane; aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, normal propylbenzene, cumene, 1,2, 3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, 1,4-diethylbenzene, 1,3-diisopropylbenzene or dodecylbenzene; halogenated aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, bromobenzene, o-dibromobenzene, 1-bromo-2-chlorobenzene, 1-bromonaphthalene, 1-chloronaphthalene, 2-chlorotoluene, 2-bromotoluene, 2,4-dichlorotoluene, 1-bromo-2-ethylbenzene, 2-chloro-o-xylene or 1,2,4-trichlorobenzene; and esters having 4 or more of carbon atoms such as propyl formate, isobutyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butylate, methyl benzoate, isopentyl benzoate or ethyl cinnamate. Any other organic solvents may be used, as long as they do not hinder the purification process of the present invention.
Of the above described organic solvents, preferable are aprotic organic solvents with permittivity 2.2 or more at 20xc2x0 C. which do not dissolve aminophosphonium chlorides having the formula (3). The preferable aprotic organic solvents include, for example, aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, normal propylbenzene, cumene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, 1,4-diethylbenzene, 1,3-diisopropylbenzene or dodecylbenzene; and halogenated aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, bromobenzene, o-dibromobenzene, 1-bromo-2-chlorobenzene, 1-bromonaphthalene, 1-chloronaphthalene, 2-chlorotoluene, 2-bromotoluene, 2,4-dichlorotoluene, 1-bromo-2-ethylbenzene, 2-chloro-o-xylene or 1,2,4-trichlorobenzene. More preferable are toluene, chlorobenzene or o-dichlorobenzene.
xe2x80x9cA solution containing at least phosphine oxides having the formula (2) and an organic solvent substantially immiscible with waterxe2x80x9d used in the purification process of the present invention means a solution containing at least the above described two components, and there may exist other components in the solution, as long as they do not hinder the purification process of the present invention. Further, the solution may be a solution formed by dissolving the above described phosphine oxides, which was once separated from another solution, in an organic solvent substantially immiscible with water.
Further, the solution may be a solution formed by removing solid aminophosphonium chlorides having the formula (3) from a liquid reaction product containing phosphine oxides having the formula (2) and the above described aminophosphonium chlorides by the solid-liquid separation process, wherein the liquid reaction product is formed by reacting iminophosphoranes having the formula (1) with phosphorus oxytrichloride using as a reaction solvent an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. which is substantially immiscible with water and does not dissolve the aminophosphonium chlorides having the formula (3), the above descried phosphine oxides and phosphonium chlorides being yielded at the same time by the above described reaction. According to the situations, the solution may be a solution formed in such a manner that, first the above described reaction is carried out using an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. as a reaction solvent, then the above described solvent is removed by, for example, the method of distilling solvent from the solution obtained by the solid-liquid separation process, which is described in the preparation process of the present invention, finally another desired organic solvent substantially immiscible with water is added instead of the above described solvent removed.
Of the above described solutions, preferable is a solution formed by removing solid aminophosphonium chlorides having the formula (3) from a liquid reaction product containing phosphine oxides having the formula (2) and the above described aminophosphonium chlorides by the solid-liquid separation process, wherein the liquid reaction product is formed by reacting iminophosphoranes having the formula (1) with phosphorus oxytrichloride using as a reaction solvent an aprotic organic solvent with permittivity 2.2 or more at 20xc2x0 C. which is substantially immiscible with water and does not dissolve the aminophosphonium chlorides having the formula (3), the above descried phosphine oxides and phosphonium chlorides being yielded at the same time by the above described reaction. And more preferable is a solution formed by removing the above described phosphonium chlorides from a liquid reaction product containing the same by the solid-liquid separation process, wherein the liquid reaction product is formed by reacting the above described phosphoranes with phosphorus oxytrichloride at the above described phosphoranes to phosphorus oxytrichloride mole ratio within 6 to 10.
As a method of water washing in the purification process of the present invention, any method can be used as long as the method allows the solution containing at least phosphine oxides having the formula (2) and an organic solvent substantially immiscible with water and water to sufficiently come in contact with each other. Usually water washing can be carried out in such a manner that first water is added to the above described solution, the solution is fully stirred, and its water phase is removed after its organic phase and water phase are separated from each other.
The amount of water used for the water washing is not expressly restricted; however, 5 weight parts or less of water is usually used per 1 weight part of the above described solution. The water washing can be carried out using such an amount of water in several installments. Preferably the water washing is carried out 2 to 5 times using 0.05 to 1.0 weight parts of water at a time per 1 weight part of the above described solution. The temperature and duration of water washing are not expressly restricted; however, the temperature is usually 10 to 80xc2x0 C., preferably 15 to 40xc2x0 C., and the duration is usually within 3 hours, preferably 0.01 to 1 hour, more preferably 0.05 to 0.5 hours.
A solution of phosphine oxides having the formula (2) which has been subjected to water washing in the above manner contains the above described phosphine oxides of a higher purity, and it can sometimes be used as it is for the next purpose. The above described phosphine oxides can be obtained as solids by concentrating to dry the solution.
According to situations, the dried solids can be further purified. The solvent used may be completely removed from the dried solids, or it may remain in the solids in a small amount. There exist a trace of impurities left dissolved in such solids even after water washing. The methods of further purifying such solids are not expressly restricted; however, a method in which one of hydrocarbons is added to the dried solids so as to dissolve phosphine oxides having the formula (2) and a trace of solids (impurities) left undissolved are removed by the solid-liquid separation process is preferable, effective and practical.
Hydrocarbons used in this method include, for example, saturated aliphatic hydrocarbons such as normal pentane, normal hexane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, normal heptane, normal octane, 2,3,3-trimethylpentane, isooctane, normal nonane, 2,2,5-trimethylhexane or normal decane; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, p-menthane, bicyclohexyl or decalin; and aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene or p-xylene.
Any other hydrocarbons may be used as long as they do not hinder this method. These hydrocarbons may be used independently or jointly. Of the above described hydrocarbons, preferable are saturated aliphatic hydrocarbons having 5 to 10 carbon atoms, such as normal pentane, normal hexane, normal heptane, normal octane, normal nonane or normal decane.
The amount of these hydrocarbons used is not expressly restricted; however, usually used are hydrocarbons 0.5 to 50 times as heavy as the above described dried solids, preferably hydrocarbons 1 to 20 times as heavy as the above described dried solids. When hydrocarbons are added to the above described dried solid to dissolve phosphine oxides having the formula (2), the temperature and duration in the above operation are not expressly restricted; however, the temperature is usually 10 to 100xc2x0 C., preferably 20 to 50xc2x0 C., the duration is usually 0.1 to 3 hours, preferably 0.5 to 2 hours. After that, the solid left undissolved in the above described hydrocarbon solution is removed by the solid-liquid separation process. The solid-liquid separation can be conducted using any methods; however, general-purpose methods such as filtration, centrifugation and decantation are usually used. Of the above methods, filtration is most preferable. The undissolved solid can be washed with hydrocarbons, and the washings may be combined to the filtrate.
Thus, a solution containing phosphine oxides having the formula (2) of a extremely high purity can be obtained. If needed, the above described solution can be concentrated to dry to obtain the above described phosphine oxides as a solid.
The present invention will be further illustrated by the following examples; however, these examples are intended to illustrate the invention and are not intended to limit the invention to the specific examples.